Device for concentration and possible purification of mineral acids, particularly sulphuric acid

Abstract

For concentration and possible purification of mineral acids, particularly sulphuric acid, a furnace which can be heated is utilized, in which one or several long quartz tubes are placed. The quartz tubes are sealed at the upper and lower parts of the furnace and inside the furnace the quartz tube is heated from the outside with the utilized means. The acid which is to be treated is fed to the respective quartz tube via the upper parts of this, and the purified acid is collected in a vessel located at the lower parts of the quartz tube. Packings of small and/or medium dimensions are arranged in the quartz tubes.

We claim: 
     
       1. An improved apparatus for concentrating and purifying liquids, comprising: a source of hot gases;   at least one elongated evaporating tube arranged upright in position to be heated by said gases, said at least one evaporating tube having an inner diameter and a height;   means for feeding liquid at the top of said at least one evaporating tube so that the liquid runs down the inner wall of said at least one evaporating tube;   packing pieces filling said at least one tube to a fraction of its height, each of said pieces having a maximum dimension in the range of from one-twentieth to one-fifth of said inner diameter, said fraction of said height being chosen so that the velocity of gases moving upward past said pieces at said fraction of said height is in the range of 1.5 to 2.0 meters per second, whereby liquid flowing down the inner wall of said at least one tube spreads over said packing pieces without flooding;   means for collecting concentrated and purified liquid at the bottom of said at least one tube;   means for conveying said gases adjacent at least a portion of said at least one evaporating tube to provide transfer of heat therebetween, said conveying means comprising inner and outer flow channels each at least partially surrounding said portion of said at least one evaporating tube, a lower portion of said outer channel being in fluid communication with a lower portion of said inner channel and an upper portion of said outer channel being in fluid communication with said source of hot gases; and   means mounted in at least one of said inner and outer channels for causing turbulation of hot gases flowing therethrough, to enhance heat transfer between said hot gases and said at least one elongated evaporating tube.   
     
     
       2. Apparatus according to claim 1, wherein said collecting means comprises a vessel into which said at least one evaporating tube extends, the height of said vessel being in the range of one-tenth to one-fifth of the height of said at least one evaporating tube and said at least one evaporating tube extending into said collecting vessel to a depth of between three-tenths and three-fifths of the height of said vessel. 
     
     
       3. Apparatus according to claim 1, wherein said pieces are pieces of quartz tubes, each piece having its diameter substantially equal to its length. 
     
     
       4. Apparatus according to claim 1, wherein a portion of said pieces having a maximum dimension of from one-eighth to one-fifth of said inner diameter are hemispheric shells having holes in the tops of their hemispheric domes, said shells being oriented in said at least one evaporating tube with the undersides of their domes facing substantially downwardly. 
     
     
       5. Apparatus according to claim 4, wherein said hemispheric shells are placed in said at least one evaporating tube with a distance between them in the range of 100 to 500 millimeters. 
     
     
       6. Apparatus according to claim 1, wherein said source comprises a furnace and said at least one evaporating tube is located in said furnace, further comprising seals surrounding said at least one evaporating tube at the upper and lower parts of said furnace, each of said seals comprising an apertured plate through which said at least one evaporating tube extends, a layer of porous, liquid resistant material applied to the outer surface of said plate, and at least one layer of tightly packed liquid resistant material applied to said porous liquid resistant material. 
     
     
       7. An improved apparatus for concentrating and purifying liquids, comprising: a source of hot gases;   at least one elongated evaporating tube arranged upright in position to be heated by said gases, said at least one evaporating tube having an inner diameter and a height;   means for feeding liquid at the top of said at least one evaporating tube so that the liquid runs down the inner wall of said at least one evaporating tube;   packing pieces filling said at least one evaporating tube, each of said pieces having a maximum dimension in the range of from one-twentieth to one-fifth of said inner diameter;   means for collecting concentrated and purified liquid at the bottom of said at least one evaporating tube;   means for conveying said gases adjacent at least a portion of said at least one evaporating tube to provide transfer of heat therebetween, said conveying means comprising inner and outer flow channels each at least partially surrounding said portion of said at least one evaporating tube, a lower portion of said outer channel being in fluid communication with a lower portion of said inner channel and an upper portion of said outer channel being in fluid communication with said source of hot gases; and   means mounted in at least one of said inner and outer channels for causing turbulation of hot gases flowing therethrough, to enhance heat transfer between said hot gases and said at least one elongated evaporating tube.   
     
     
       8. Apparatus according to claim 7, wherein said collecting means comprises a vessel into which said at least one evaporating tube extends, the height of said vessel being in the range of one-tenth to one-fifth of the height of said at least one evaporating tube and said at least one evaporating tube extending into said collecting vessel to a depth of between three-tenths and three-fifths of the height of said vessel. 
     
     
       9. Apparatus according to claim 7, wherein said pieces are pieces of quartz tubes each piece having its diameter substantially equal to its length. 
     
     
       10. Apparatus according to claim 7, wherein a portion of said pieces having a maximum dimension of from one-eighth to one-fifth of said inner diameter are hemispheric shells having holes in the tops of their hemispheric domes, said shells being oriented in said at least one evaporating tube with the undersides of their domes facing substantially downwardly. 
     
     
       11. Apparatus according to claim 10, wherein said hemispheric shells are placed in said at least one evaporating tube with a distance between them in the range of 100 to 500 millimeters. 
     
     
       12. Apparatus according to claim 7, wherein said source comprises a furnace and said at least one evaporating tube is located in said furnace, further comprising seals surrounding said at least one evaporating tube at the upper and lower parts of said furnace, each of said seals comprising an apertured plate through which said at least one tube extends, a layer of porous, liquid resistant material applied to the outer surface of said plate, and at least one layer of tightly packed liquid resistant material applied to said porous liquid resistant material. 
     
     
       13. An improved apparatus for concentrating and purifying liquids, comprising: a source of hot gases;   at least one elongated evaporating tube arranged upright in position to be heated by said gases, said at least one evaporating tube having an inner diameter and a height;   means for feeding liquid at the top of said at least one evaporating tube so that the liquid runs down the inner wall of said at least one evaporating tube;   packing pieces filling said at least one evaporating tube, said pieces comprising medium pieces each having a maximum dimension in the range from one-eighth to one-fifth of said inner diameter, and large pieces each having a maximum dimension in the range of from one-fourth to one-half of said inner diameter;   means for collecting concentrated and purified liquid at the bottom of said at least one evaporating tube;   means for conveying said gases adjacent at least a portion of said at least one evaporating tube to provide transfer of heat therebetween, said conveying means comprising inner and outer flow channels each at least partially surrounding said portion of said at least one evaporating tube, a lower portion of said outer channel being in fluid communication with a lower portion of said inner channel and an upper portion of said outer channel being in fluid communication with said source of hot gases; and   means mounted in at least one of said inner and outer channels for causing turbulation of hot gases flowing therethrough, to enhance heat transfer between said hot gases and said at least one elongated evaporating tube.   
     
     
       14. Apparatus according to claim 1, 7 or 13, wherein said inner and outer flow channels are defined by a tube unit having an inner tubular wall spaced from said evaporating tube to define said inner flow channel and an outer tubular wall spaced from said inner tubular wall to define said outer flow channel, whereby said gases heat said inner and outer walls to cause them to radiate heat to said evaporation tube. 
     
     
       15. Apparatus according to claim 14, wherein said means for causing turbulation comprises at least one guide vane mounted in said outer flow channel and attached to at least one of said inner and outer walls, each said guide vane extending around a portion of the circumference, along a portion of the length and across a portion of the width of said outer flow channel. 
     
     
       16. Apparatus according to claim 15, wherein said guide vanes extend around one-fourth of said circumference, at approximately a 45° angle to the horizontal and across from 80 to 90 percent of the width of said outer flow channel. 
     
     
       17. Apparatus according to claim 13, wherein said medium pieces are positioned below said large pieces in said at least one evaporating tube. 
     
     
       18. Apparatus according to claim 13, further comprising small pieces having a maximum dimension in the range of one-twentieth to one-eighth of said inner diameter. 
     
     
       19. Apparatus according to claim 13, wherein said large pieces have a maximum dimension of approximately one-third of said inner diameter. 
     
     
       20. Apparatus according to claim 17, wherein said collecting means comprises a vessel into which said at least one evaporating tube extends, the height of said vessel being in the range of one-tenth to one-fifth of the height of said at least one evaporating tube and said at least one tube extending into said collecting vessel to a depth of between three-tenths and three-fifths of the height of said vessel. 
     
     
       21. Apparatus according to claim 13, wherein said pieces are pieces of quartz tubes each piece having its diameter substantially equal to its length. 
     
     
       22. Apparatus according to claim 13, wherein a portion of said large pieces are hemispheric shells having holes in the tops of their hemispheric domes, said shells being oriented in said at least one evaporating tube with the undersides of their domes facing substantially downwardly. 
     
     
       23. Apparatus according to claim 22, wherein said hemispheric shells are placed in said at least one evaporating tube with a distance between them in the range of 100 to 500 millimeters. 
     
     
       24. Apparatus according to claim 13, wherein said source comprises a furnace and said at least one evaporating tube is located in said furnace, further comprising seals surrounding said at least one tube at the upper and lower parts of said furnace, each of said seals comprising an apertured plate through which said at least one evaporating tube extends, a layer of porous, liquid resistant material applied to the outer surface of said plate, and at least one layer of tightly packed liquid resistant material applied to said porous liquid resistant material. 
     
     
       25. Apparatus according to claim 6, 12 or 24, wherein said apertured plate at said lower part of said furnace is fire resistant cast iron.